The major long-term objective of this project is the synthesis of the major metabolite of delta-l-tetrahydrocannabinol and various analogs. The route to be investigated uses dienes prepared by a Wittig reaction from phosphonium salts derived from 2,3-dihalopropenes for a Diels-Alder reaction to prepare the key vinyl halide intermediate. This compound is then converted into the appropriate dihydropyran cannabinoid skeleton using trimethylailyl iodide, chemistry which was discovered in an earlier synthesis of the primary cannabinoids. The synthesis is completed by carboxylation of the vinyl halide via an organometallic reagent.